The invention relates to an apparatus for facing and internal turning comprising a rotationally driven shaft, a turning head fixed for rotation with the shaft, and a tool carriage for carrying a cutting tool displaceable on the turning head transversely to the axis of rotation thereof.
In a known apparatus of this kind (DE-OS No. 16 52 658), transverse displacement of the tool carriage is effected by first and second planetary gear units lying in different planes extending at right angles to the axis of rotation of the shaft, the sun gear of the first planetary gear unit being fixed for rotation with the shaft and the sun gear of the second planetary gear unit being rotatable relative to the shaft and acting as a driving gear for the tool carriage. The two planetary gear units are selectively coupled to one another by one of a plurality of worm gear trains having different transmission ratios, so that depending on the worm gear train selected the transverse displacement of the tool carriage and of the tool connected to it is effected more or less quickly.
The manufacture of worm gear trains entails considerable labour and expense. In an apparatus of the type in question such gear trains also have the disadvantage of requiring considerable space, so that they have an unfavourable effect on the overall size of the apparatus.
The problem underlying the present invention is that of remedying these shortcomings and indicating simple, space-saving means with the aid of which automatic transverse displacement of the tool carriage can be initiated.